The bomb scare at the US embassy in central Oslo on Tuesday was caused by forgetful embassy staff leaving a dummy bomb under a parked vehicle, according to Oslo police.

The embassy called the police at around 11.30am on Tuesday morning to report that a suspicious package had been spotted.

The Oslo police bomb squad was swiftly dispatched to the scene and was able to conclude that the item was harmless.

According to a police statement it had been concluded that the item belonged to the embassy and was intended for training purposes. Embassy staff had simply forgotten to remove it from under the parked car.